Spakk ignition apparatus



y 18, 9 N. A. PARISH 3,184,639

SPARK IGNITION APPARATUS Filed Oct. 2, 1961 United States Patent 3,184,639 SPARK IGNI'HQN APPARATUS Norman Arthur Parish, Hemel Hempstead, England, assignor to Borax Limited, London, England Filed Get. 2, 1961, Ser. No. 142,123 Claims priority, application Great Britain, Oct. 11, 196i), 34,823/60 2 Ciaims. (Cl. 315209) This invention relates to spark ignition apparatus of the kind comprising a transformer having a primary and a secondary winding, an interrupter through which the primary winding is adapted for connection to a source of direct or rectified alternating current, said interrupter being normally urged towards a closed position but movable to an open position by electromagnetic forces resulting from current flow in the primary winding, a capacitor connected across the secondary winding, and a control gap and spark gap connected in series across the capacitor.

With such apparatus the sparking voltage is determined by the voltage at which the control gap commences to conduct. -In certain applications it is found that under some conditions the required energy of the spark must be considerably in excess of that normally required. Thus, for example, on an aircraft a six joule spark will suifice for most purposes, but when the ambient temperature is low or the aircraft is flying at a high altitude a twelve ioule spark may be required. Clearly, it is uneconomical to utilise a control gap passing a spark at a constant energy of twelve joules, and the object of the present invention is to provide spark ignition apparatus of the kind specified in a convenient form whereby this difiiculty can be overcome.

According to the invention, spark ignition apparatus of the kind specified includes means for reducing the voltage at which the control gap conducts whilst maintaining the spark rate substantially constant.

An example of the invention is illustrated diagrammatically in the accompanying drawing.

Referring to the drawing there is provided a pair of terminals 1, 2 adapted for connection to a source of direct or rectified alternating current. The terminals are interconnected through the primary winding 3 of a transformer 4 and an interrupter 5 which is bridged by a capacitor 6. The interrupter is of the kind which is urged towards its closed position, in which it permits current fiow to the primary winding 3, by resilient means in the form of a spring S, and is movable to the open position by electro-magnetic forces resulting from current flow in the primary winding 3.

The secondary winding 7 of the transformer is bridged by a circuit containing one or more rectifiers 8 and a capacitor 9, whilst the capacitor 9 is bridged by a control gap '10, an inductor 11 and a spark gap 12 connected in series. Further, the inductor 11 and spark gap 12 are bridged by a resistor 13.

The control gap is mounted in an hermetically sealed envelope 14, and surrounding the control gap either internally or externally of the envelope 14 is a metallic band 15 which is connected through a normally closed contact 16 of a relay, to a point intermediate the spark gap 12 and the resistor 13. Further, the coil 17 of the relay is connected between the terminals 1, 2 through a manually operable switch 18.

Where the band 15 is inside the envelope 14 it may be connected to either electrode of the control gap 10. However, where as shown the band 15 is outside the envelope 14 it must be connected to the positive electrode of the control gap 10 as it is, in the example described, through the contact 16 and resistor 13.

The arrangement is such that when the manually operable switch 18 is closed the contact 16 is open and the ice band 15 has no efiect. However, when the switch 18 is opened, the contact 16 is closed and the band 15 reduces the voltage at which the control gap 10 commences to conduct.

With the arrangement so far described reduction in the operating voltage of the control gap 10 will be accompanied by an increase in the spark rate. In order to maintain the latter frequency substantially constant, the strength of the interrupter spring S is adjusted so that the desired frequency is obtained at the lower voltage. Further, there is connected in parallel with the relay winding 17 an auxiliary coil 19 which is wound on the core of the transformer 4 so as to assist the action of the interrupter spring S when the switch 18 is closed, i.e. at the higher voltage. By suitable adjustment of the auxiliary coil 19 the spark rate can be maintained substantially constant at the higher and lower voltages.

Although apparatus in accordance with the invention is primarily intended for use in aircraft, it may also be used in other applications such, for example, as road vehicles and industrial furnaces.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Spark ignition apparatus comprising in combination first and second terminals for connection to a DC. source, a transformer having a primary winding and a secondary winding, a capacitor connected across said secondary winding in a series circuit including a rectifier, a control gap and a spark gap connected in a series circuit across said capacitor, means connecting one end of said primary winding to said second terminal, an interrupter through which the other end of said primary winding is connected to the first terminal, resilient means normally urging said interrupter to a closed position, means operable by electromagnetic forces derived from current flow in said primary winding for urging said interrupter towards its open position against the action of said resilient means, an additional winding having its ends normally connected to said first and said second terminal respectively, means responsive to current flowing in said additional winding for assisting the action of said resilient means, means for reducing the breakdown voltage of said control gap and means operable when the breakdown voltage of said control gap is reduced for disconnecting said additional winding from the first and second terminals, the frequency of operation of said interrupter being determined by the primary winding and said additional winding and said resilient means, and disconnection of said additional winding tending to maintain the spark rate substantially constant when the breakdown voltage of said control gap is reduced.

2. Spark ignition apparatus comprising in combination a pair of terminals for connection to a 13.0 source, a transformer having a core and a primary winding, a secondary winding and additional winding wound on said core, a capacitor connected across said secondary winding in a series circuit including a rectifier, a control gap and a spark gap connected in series across said capacitor, said control gap including a pair of spaced electrodes, a metallic band associated with said control gap, means connecting said metallic band to one of the electrodes of the control gap, said means including a normally closed relay contact, a relay coil and a manually operable switch connected across said supply terminals in series, means connecting one end of said additional winding to one of the supply terminals and the other end of said additional winding to a point intermediate the manually operable switch and the relay coil, means connecting one end of said primary winding to one of the supply terminals, an interrupter through which the other end of the primary winding is connected to the other supply terminal, resilient means acting to close said interrupter, means responsive to electromagnetic forces derived from current flowing in said primary winding for opening said interrupter against the action of said resilient means, means whereby electromagnetic forces derived from current flowing in said additional winding for assisting the action of said resilient means, the frequency of operation of said interrupter being determined by the primary winding, the additional winding and said. spring, said manually operable switch acting when closed to energise the relay and open said relay contact and connect said additional winding to the supply terminals, and said manually operable switch operating when open to deenergise the relay, close said relay contact to reduce the breakdown voltage of said control gap, and disconnect said additional Winding from the supply terminals, disconnection of said additional Winding from the supply terminals tending to maintain the 4 spark rate substantially constant by varying the frequency of operation of said interrupter.

References Cited by the Examiner 5 UNITED STATES PATENTS 2,651,005 9/53 Tognola 3l5-209 2,837,698 6/58 Segall 3'15-209 7 2,938,147 5/60 Rose 315-209 10 FOREIGN PATENTS 1,101,861 3/61 Germany.

DAVID J. GALVIN, Primary Examiner.

15 JAMES D. KALLAM, Examiner. 

1. SPARK IGNITION APPARATUS COMPRISING IN COMBINATION FIRST AND SECOND TERMINALS FOR CONNECTION TO A D.C. SOURCE, A TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING A CAPACITOR CONNECTED ACROSS SAID SECONDARY WINDING IN A SERIES CIRCUIT INCLUDING A RECTIFIER, A CONTROL GAP AND A SPARK GAP CONNECTED IN A SERIES CIRCUIT ACROSS SAID CAPACITOR, MEANS CONNECTING ONE END OF SAID PRMIARY WINDING TO SAID SECOND TERMINAL, AN INTERRUPTER THROUGH WHICH THE OTHER END OF SAID PRIMARY WINDING IS CONNECTED TO THE FIRST TERMINAL, RESILIENT MEANS NORMALLY URGING SAID INTERRUPTER TO A CLOSED POSITION, MEANS OPERABLE BY ELECTROMAGNETIC FORCES DERIVED FROM CURRENT FLOW IN SAID PRIMARY WINDING FOR URGING SAID INTERRUPTER TOWARDS ITS OPEN POSITION AGAINST THE ACTION OF SAID RESILIENT MEANS, AN ADDITIONAL WINDING HAVING ITS END NORMALLY CONNECTED TO SAID 